Fire differentially affects mortality and seedling regeneration of three woody invaders in forest–grassland mosaics of the southern Western Ghats, India

Abstract

This is a repository copy of Fire differentially affects mortality and seedling regeneration of three woody invaders in forest-grassland mosaics of the southern Western Ghats, India.

Restoring tropical forest–grassland mosaics invaded by woody exotics

“…Controlled fires can be used to clear woody biomass in many cases (Grace et al 2001), as well as to deplete soil seed banks of invasive plants (DiTomaso et al 2006), and to volatilize excess nutrients (Blair 1997). On the other hand, fires can also encourage secondary invasion in some cases, particularly if fire breaks invasive seed dormancy or if invasives regenerate post‐fire, and employing other techniques such as manual weeding, mowing and herbicide application may be needed to prevent re‐invasion in such cases (Nsikani et al 2019; Sriramamurthy et al 2020). Finally, clearing invasives can be an employment‐generating activity, and cleared biomass can be used as a resource by local communities or businesses to increase cost‐effectiveness further (e.g.…”

“…At least 40 exotic plant species were introduced in the Nilgiris in the 19th and early 20th centuries, of which three woody N‐fixers have become invasive in the montane grasslands ( Acacia mearnsii , Cytisus scoparius , and Ulex europaeus ; Joshi et al 2018; Sriramamurthy et al 2020). Invasion by these woody N‐fixers has decreased the area of the Nilgiri grasslands by 50–60% from 1973 to 2017 (Arasumani et al 2019), and experimental studies predict further invasion due to climate change (Joshi et al 2020).…”

“…Fire, in combination with post‐fire management to prevent re‐invasion (Le Maitre et al 2011), can potentially be a useful tool to cost‐effectively clear and manage invasion by A. mearnsii and C. scoparius in the Nilgiris, which demonstrate high adult mortality post‐fire (I.4., Srinivasan et al 2012; Sriramamurthy et al 2020). Further, inorganic N‐availability and N‐mineralization rates in burnt areas drop to levels comparable to uninvaded grasslands (M. Raghurama & M. Sankaran, unpublished data).…”

“…Further, inorganic N‐availability and N‐mineralization rates in burnt areas drop to levels comparable to uninvaded grasslands (M. Raghurama & M. Sankaran, unpublished data). However, USOs of U. europaeus regenerate post‐fire with coppicing individuals flowering within a year following fire in the Nilgiris, and fire could facilitate further invasion by this species (Sriramamurthy et al 2020). So, fire is likely to be an effective management tool only in areas without U. europaeus and should be used carefully in the landscape.…”

Patterns and consequences of invasion of tropical montane forests by Cestrum aurantiacum Lindl. in the Western Ghats

“…While one of main species of exotic plantation trees, Acacia mearnsii, itself is a dominant and aggressive invader of the remnant natural grasslands (Thomas and Palmer, 2007;Arasumani et al, 2019), other woody invasive shrubs, including scotch broom Cytisus scoparius and common gorse Ulex europaeus have also invaded the grasslands extensively in recent years (Sriramamurthy et al, 2022). While these woody invasions of the grasslands have received lot of research attention (Joshi et al, 2018;Arasumani et al, 2019;Sriramamurthy et al, 2020), far less research attention has been paid to the less visible invasions, often in the understoreys, of shola forest patches. This is an important knowledge gap, as the patterns and consequences of invasions within shola forests are likely to differ from those in grasslands, such that the management of invasives in the sholas versus the grasslands, will require different strategies.…”